Homo habilis remains, such as those from Olduvai Gorge, are much more recognisable as humans. Stone-tool use was developed by these people around 2.5 million years ago before they were replaced by Homo erectus about 1.5 million years ago. Members of Homo habilis used Olduwan tools and had learned to control fire to support the hunter-gatherer method of subsistence.
The carrier species from Africa to Europe undoubtedly was Homo erectus. This type of human is more clearly linked to the flake tradition, which spread across southern Europe through the Balkans to appear relatively densely in southeast Asia. Many Mousterian finds in the Middle Paleolithic have been knapped using a Levallois technique, suggesting that Neanderthals evolved from Homo erectus.
Also in Europe appeared a type of human intermediate between Homo erectus and Homo sapiens, typified by such fossils as those found at Swanscombe, Steinheim, Tautavel, and Vertesszollos (Homo palaeohungaricus). Although it is unwise, given the current state of knowledge, to assume an exclusive association of any type of human with any specific type of tool, the intermediates seem responsible for the hand-axe tradition. Such an association does not imply that they necessarily evolved in Europe.
Flakes and axes coexisted in Europe, sometimes at the same site. The axe tradition, however, spread to a different range in the east. It appears in Arabia and India, but more importantly, it does not appear in southeast Asia.